ZINC FINGER PROTEIN 1 and 8 interact with polycomb repressive complex 2 to repress class B and C floral organ identity genes

Precise control of gene expression is essential for establishing and maintaining cell identities in response to endogenous signals and environmental cues in multicellular organisms. An example is the regulation of the class B and C floral organ identity genes-APETALA3 (AP3), PISTILLATA (PI), and AGAMOUS (AG)-which are repressed in leaves and activated in floral meristems. Their repression in leaves is associated with CURLY LEAF (CLF), a core component of the polycomb repressive complex 2 (PRC2). However, since CLF is expressed in both leaf and floral primordia, its target specificity is likely mediated by additional factors. In this study, we found that ZINC FINGER PROTEIN 1 (ZP1) and ZFP8 physically interact with PRC2 components CLF, SWINGER (SWN), and FERTILIZATION-INDEPENDENT ENDOSPERM (FIE) to repress AP3, PI, and AG. In plants ectopically expressing ZP1 and ZFP8, loss of CLF partially restored floral organ identity and reactivated the expression of AP3, PI, and AG, indicating that this repression is PRC2-dependent. Functional studies revealed that the zinc finger domain is necessary and sufficient for ZFP8 activity, whereas both the zinc finger and EAR domains are required for ZP1 function.